The famous Roman legion IX Hispana was founded around 81 to 72BC by Sertorius or Pompeius Magnus. It served with distinction under him and Julius Casear during his time in Spain, when he raised his own famous Legio X as the sister legion to IX. The title Hispana was awarded by Augustus for distinguished service during his campaigns in northern Spain and Portugal in the late twenties BC. The legion came to Britain in 43AD but after a series of successful campaigns in the first twenty years, it met its match against the Iceni and Queen Boudicca in the famous revolt of 60/61AD. Its commander Petilius Ceralis escaped with his cavalry and left the understrength legion to perish at the hands of the British mob. The legion was not cashiered and it was sent replacements and its Legate went on to serve with distinction in later campaigns. The legion disappears from view about 160AD, when it apparently went down fighting against the Parthians. There are rumours it diappeared across Hadrian's Wall around 130AD but this is unlikely. It did though seem to suffer rather more than the other legions in Britain and was apparently hated more than the others. 
The Romans were great engineers. Much of this expertise came from the army. The legions had all kinds of experts to call upon, from basic brick layers to skilled surveyors and hydraulic engineers. It was the army that first opened up a province to the full benefits of Roman civilisation.
The Roman soldier had to be far more than just a killer. He was first and foremost a citizen of a Republic and a privileged person protected in law. Furthermore his example to provincials encouraged others to seek the valuable Roman citizenship so that they too could become Romans. This meant that the legionary also had to be a diplomat.
Good relations between ruler and ruled were far preferable to perpetual revolt tying down large bodies of men. Britain had upwards of four legions and an equal number of auxilia to keep the peace. In Africa and Spain there was but one Legion to keep these provinces quiet!
